Colorless allyl diglycol carbonate

ABSTRACT

Composition of matter and process for imparting a colorless appearance to cast allyl diglycol carbonate articles such as lenses and lens blanks and for simultaneously imparting to the article an ability to fluoresce when subjected to ultraviolet light. The composition comprises about 40 parts maleic anhydride, maleic acid, copolymers of propylene glycol with maleic acid or maleic anhydride, or mixtures thereof, and between about 0.5 and 1.5 parts of a mixture of 10 parts cobalt acetyl acetonate and between about 0.4 parts to 1.2 parts copper acetyl acetonate. Between about 0.05 and 0.15 parts of the composition is mixed with 1600 parts allyl diglycol carbonate monomer-catalyst prepolymer mixture and cast to form the desired article.

BACKGROUND OF THE INVENTION

This invention relates to a composition of matter which may be added toconventional allyl diglycol carbonate resins to impart a colorlessappearance to optically clear allyl diglycol carbonate articles such aslenses and lens blanks produced therefrom.

Allyl diglycol carbonate resins have been extensively used to formoptically clear, ophthalmic quality lens blanks and lenses. While suchresins provide a highly desirable material for manufacturing sucharticles, they are characterized by a faint but obviously noticeableyellow color which makes them readily distinguishable from glass.Attempts to formulate prepolymer mixtures which appear "colorless" whenpolymerized have not been successful. The term "colorless" as usedhereinafter, refers to a glass-like appearance, i.e., a very slightbluish tinge such as that possessed by glass lenses when viewed from theside.

Furthermore, with the increase in the number of allyl diglycol carbonateophthalmic quality lenses manufactured, it has become increasingly moredifficult for any one manufacturer to identify his products after sale.In this regard, it would be highly desirable for an individualmanufacturer to be able to quickly and easily identify his products fromthose of competitors when a lens is returned for repair or replacement.

The composition of matter of the instant invention, when incorporatedinto conventional allyl diglycol carbonate articles, not only impartsthe desired colorless appearance, but also imparts a faint but distinctultraviolet activated fluorescence to the product which enables simpleand rapid identification thereof.

SUMMARY OF THE INVENTION

At the heart of the instant invention is the discovery that acombination of two well-known plastic colorants, i.e., cobalt acetylacetonate and copper acetyl acetonate, when mixed in certain proportionswith maleic acid, maleic anhydride, or copolymers of certain glycolswith maleic anhydride or maleic acid, can, when added in effectiveamounts to conventional allyl diglycol resins, impart to articles madetherefrom both a colorless appearance and the ability to fluoresce whenexposed to ultraviolet radiation. The copper acetyl acetonate aloneimparts a greenish blue tint, the cobalt acetyl acetonate alone impartsa pink to rust tint. However, a proper combination of these twocolorants together with such resins as monopropylene glycol monomaleatecomprise a "colorless concentrate" which enables the manufacture ofarticles which are free from the characteristic yellow color of sucharticles and which, from a visual standpoint, are virtuallyindistinguishable from glass articles.

In the preferred embodiments of the invention, a concentrate is providedwhich comprises about 40 parts of a substance selected from the groupconsisting of maleic anhydride, maleic acid, copolymers of propyleneglycol with maleic anhydride or maleic acid, and mixtures thereof, andbetween about 0.5 and 1.5 parts of a mixture consisting of about 10parts cobalt acetyl acetonate and between 0.4 and 1.2 parts copperacetyl acetonate. A still more preferred concentrate compositioncomprises 40 parts of a copolymer consisting of the product of reactionof substantially equimolar quantities of propylene glycol with maleicanhydride, about 0.9 parts cobalt acetyl acetonate, and about 0.07 partscopper acetyl acetonate.

The concentrate may be added, as such, to allyl digylcol carbonateresins, in the proportion of 16 parts resin to between 0.05 and 0.15parts concentrate. After incorporation and thorough mixing of theconcentrate with the resin, optically clear articles may be formed byvarious well-known techniques, e.g., casting, to provide colorlessarticles virtually indistinguishable on visual observation from glass.

In addition, when articles formed as disclosed above are exposed toultraviolet radiation, they exhibit a faint but distinctive fluoresencewhich provides a simple and effective method of identifying the articlesafter they have been commercially distributed. To further increase thefluorescence, a fluorescent dye may also be included in the prepolymercomposition in a concentration of less than about 10 parts per million,preferably about 0.25 parts per million, without affecting the color.

Alternatively, the process of the invention may be practiced by addingeach of the components disclosed above, in proper proportions, directlyto a ready-to-use prepolymer without first formulating a concentrate.

Accordingly, it is an object of the invention to provide a method ofproducing allyl diglycol carbonate articles which exhibit a colorlessappearance.

Another object of the invention is to provide a composition of matterwhich may be easily formulated from inexpensive materials forincorporation into conventional allyl diglycol carbonate resins toremove the yellow color normally present in products cast therefrom.

Another object of the invention is to provide a simple method ofuniquely identifying allyl diglycol carbonate articles after they havebeen commercially distributed.

Still another object of the invention is to provide a process forforming a colorless, optically clear, allyl diglycol carbonate article,e.g., an ophthalmic quality lens or lens blank.

Other objects and features of the invention will be apparent from thefollowing description of some preferred embodiments.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

At the outset, the invention is described in its broadest overall aspectwith a more detailed description following.

It is believed that prior art attempts to remove the yellow colornaturally present in resins such as allyl digylcol carbonate havegenerally been successful only where another color has been substitutedfor the characteristic yellow color. In contrast, the present inventionprovides a composition which can neutralize the yellow color to yield acolorless cast allyl diglycol carbonate article. The composition ofmatter of the invention may be formulated as a concentrate andthereafter added directly to the prepolymers in amounts disclosed belowto produce the colorless articles. Alternatively, the individualcomponents of the concentrate may be added separately and directly tothe prepolymer to achieve the same effect. However, the prior procedureis preferred since the small but critical amounts of the components ofthe composition of the invention are easier to incorporate in theprepolymer mixtures if they are first mixed as a batch of concentrate.

Three components are essential to the composition of the invention. Thefirst is cobalt acetyl acetonate, a known colorant which alone insufficient concentration imparts a pink to rust tint to allyl diglycolcarbonate polymers and copolymers of allyl diglycol carbonate withmaleates. The second component is copper acetyl acetonate which alone insufficient concentration imparts a greenish blue tint to these resins.The third component comprises maleic acid, maleic anhydride, and/orcopolymers of propylene glycol, ethylene glycol, or glycerin with maleicanhydride or maleic acid. The presence of one or more of these lattersubstances with the combination of the cobalt and copper acetonates inproper proportion alters the coloring characteristic of each of thecolorants, or in some way interacts with the colorants, to produce asubstance which effectively neutralizes the natural yellow color of castallyl diglycol carbonate articles.

The relative amounts of these three substances in the concentrate of theinvention are as follows: 40 parts resinous material selected from amongthose indicated above; and between about 0.5 and 1.5 parts of a mixtureof 10 parts cobalt acetyl acetonate and between 0.4 and 1.2 parts copperacetyl acetonate. A preferred composition comprises 40 parts of theproduct of reaction of substantially equimolar quantities of propyleneglycol with maleic anhydride, 0.9 parts cobalt acetyl acetonate, andabout 0.07 parts copper acetyl acetonate.

Between about 0.05 and 0.15 parts of this composition is then added toabout 16 parts allyl diglycol carbonate containing a catalyst such asisopropyl percarbonate. A trace amount of an ultraviolet absorber(optional) and .25 parts per million of a fluorescent dye such as thatsold under the trademark Uvitex-OB may also be added if desired.

The invention will be further understood from the following exampleswhich in no event should be construed as limiting.

EXAMPLE 1

A lens forming composition comprising 800 grams of the allyl diglycolcarbonate resin sold under the tradename CR-39, 0.0175 grams of copperacetyl acetonate, 4.0 grams of monopropylene glycol monomaleate(hereinafter MPGMM), 0.20 grams of UVA #9 (2 hydroxy benzophenone,American Cyanimide), and 25 grams of isopropyl percarbonate wereblended, filtered, and cast by conventional techniques to form lensblanks. After curing, the products exhibited a light bluish-green tint.No yellow color could be observed, but it had been replaced by thegreenish blue color characteristic of the metallo-organic dye.

EXAMPLE 2

800 grams of CR-39, 0.08 grams of cobalt acetyl acetonate, 4.0 grams ofMPGMM, 0.2 grams UVA #9, and 25 grams of isopropyl percarbonate wereblended and cast by conventional techniques. The lens blanks producedhad a pink to rust tinge which effectively masked the natural yellowcolor of the untinted material.

EXAMPLE 3

A prepolymer mix consisting of 800 grams of CR-39, 4 grams MPGMM, 0.12grams cobalt acetyl acetonate, 0.20 grams UVA #9, and 25 grams isopropylpercarbonate was prepared as disclosed above. A second prepolymer mixidentical to the first except that .015 grams copper acetyl acetonatewas substituted for the cobalt acetonate was also prepared. These twoprepolymer mixes were then blended in a 50/50 ratio by weight. The blendwas stirred and cast into blanks, minus lenses, and plus lenses. Thecast products had a good, clear colorless appearance when compared tothe products cast without the colorants. When subjected to ultravioletlight, these products exhibited a faint but detectable fluoresence.

EXAMPLE 4

Using the composition of Example 3, the following variables were testedto determine their effect on the lenses and the following results wereobtained.

    ______________________________________                                        PARAMETER   VARIATION     Result                                              ______________________________________                                        % catalyst included                                                                       2.77 - 3.25   no effect on color                                  Curing cycle                                                                              overnight cycle to                                                            rapid 5 hour cycle                                                                          no effect on color                                  % methyl methacry-                                                            late included                                                                             0% to 40%     no effect on color                                  Picking time                                                                              picked at 10% to                                                              50% Dye Rate Cure                                                                           no effect on color                                  Air aging   Run in parallel                                                               with conventional                                                             CR-39 lenses for up                                                           to 250 hours  no effect on color                                              Time (Hr.)                                                        Humidity Aging at                                                                          24           Exhibited excellent                                 190 ° F (100% rel.                                                                  48           color stability                                     humidity)    72           comparable or great-                                            100           er than convention-                                                           al polycarbonate                                                              articles                                            Roof Exposure                                                                             30 days on roof                                                                             no effect on color                                  "Fadeometer"                                                                              100 hours in                                                      testing*    Fadeometer    no effect on color                                  ______________________________________                                         *Commercially available accelerated aging apparatus                      

EXAMPLE 5

The procedure of Example 3 was repeated except that an approximatelyequimolar mixture of propylene glycol and maleic anhydride, blended byconventional techniques, was substituted for the MPGMM. The opticallyclear products made with the procedure and formulation of this exampleexhibited a color which was indistinguishable from that of the productsof Example 3.

EXAMPLE 6

The procedure of Example 3 was repeated, except that the MPGMM wasomitted. Cast products made from this formulation exhibited a color thatwas initially very similar to the normal yellow tinged products of theprior art. Furthermore, when subjected to humidity aging such as thatdisclosed in Example 4, these lenses were observed to have much lessstable color than the formulations which included the MPGMM. Of thevarious monomers useful in the invention, the most stable color isproduced when a mixture of proplyene glycol and maleic anhydride isused.

EXAMPLE 7

A prepolymer mix was prepared using 386.4 grams of CR-39, 13.6 grams ofisopropyl percarbonate, 1.2 grams of maleic anhydride, 1.2 grams ofpropylene glycol, 0.05 grams of cobalt acetyl acetonate, 0.0055 grams ofcopper acetyl acetonate, and 0.10 grams of UVA #9. This compositionproduced cast products having a colorless appearance which was stablewhen subjected to humidity testing.

EXAMPLE 8

The procedure of Example 9 was repeated except that an equal amount ofmaleic acid was substituted for the maleic anhydride. The cast productsmade from this composition were indistinguishable from the products ofExample 7.

EXAMPLE 9

In order to promote ease of handling and standardization of theconcentrations of colorants in the allyl diglycol carbonate castarticles, concentrates have been prepared which may be added to thecarbonate monomer-polymerization catalyst mixture to impart the desiredeffect. One successful concentrate was formulated as follows:

174 grams of propylene glycol, at 140° F, were mixed with 226 grams ofmaleic anhydride at the same temperature. After blending thesecomponents and allowing them to react, 0.74 grams of copper acetylacetonate and 9.0 grams of cobalt acetyl acetonate were added thereto.The mixture was warmed and stirred until all metallic salts had beendissolved and was thereafter filtered through a medium porosity filter.

9.3 grams of this concentrate was then added to a prepolymer compositioncomprising 1,655 grams of allyl diglycol carbonate mixed with isopropylpercarbonate. This prepolymer mix was stirred and filtered through a 7to 10 micron Millipore filter before casting. The mixture producescolorless lenses and lens blanks of normal hardness.

EXAMPLE 10

The procedure of Example 9 was repeated except that Ciba-GeigyUvitex-OB, a fluorescent dye which is activated by ultraviolet light togive off a blue color, was added to the concentrate so that its finalconcentration in the cast product was about 0.25 parts per million. Theaddition of this substance had no effect on the properties of the castproducts other than to reinforce the weak fluorescence which naturallyoccurs in the articles containing the composition of the invention. Theaddition of the dye makes the identification procedure moredeterminative. Other fluorescent dyes could be used for this purpose,and in fact, the dye is an optional ingredient which could be omitted.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative, and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

I claim:
 1. An optically clear, colorless, ophthalmic quality lenscomprising about 16 parts allyl diglycol carbonate and between about0.05 and 0.15 parts of a composition comprising 40 parts of a memberselected from the group consisting of maleic anhydride, maleic acid, theproducts of reaction of propylene glycol, ethylene glycol, and glycerinwith maleic anhydride or maleic acid, and mixtures thereof, and betweenabout 0.5 and 1.5 parts of a mixture consisting essentially of 10 partscobalt acetyl acetonate and between 0.4 and 1.2 parts copper acetylacetonate.
 2. The lens as set forth in claim 1 further comprising afluorescent dye present in a concentration less than about 10 parts permillion.
 3. The lens as set forth in claim 1 wherein said member ismonopropylene glycol monomaleate.
 4. The lens as set forth in claim 1comprising about 0.09 parts of said composition.
 5. An optically clear,colorless, ophthalmic quality lens consisting essentially of 1600 partsallyl digylcol carbonate, between about 5 and 15 parts of the product ofreaction of propylene glycol and maleic anhydride, between 0.1 and 0.3parts cobalt acetyl acetonate, and between about 0.005 and 0.03 partscopper acetyl acetonate.
 6. The lens as set forth in claim 5 comprising9 parts monopropylene glycol monomaleate, about 0.20 parts cobalt acetylacetonate, and about 0.015 parts copper acetyl acetonate.
 7. The lens asset forth in claim 5 further comprising a trace amount of a compatibleultraviolet absorber.
 8. A process for forming a colorless, opticallyclear allyl diglycol carbonate article, said process being characterizedby the steps of:1. providing a polymerizable allyl diglycol carbonateprepolymer containing a polymerization catalyst;
 2. providing acolorless concentrate comprising about 40 parts of a member selectedfrom the group consisting of maleic anhydride, maleic acid, the productsof reaction of propylene glycol, ethylene glycol and glycerin withmaleic acid, the products of reaction of propylene glycol, ethyleneglycol, and glycerin with maleic anhydride, and mixtures thereof, andbetween about 0.5 and 1.5 parts of a mixture consisting essentially of10 parts cobalt acetyl acetonate and between 0.4 and 1.2 parts copperacetyl acetonate;
 3. mixing 16 parts of said prepolymer with between0.05 and 0.15 parts of said concentrate; and
 4. shaping and curing themixture produced in step 3 to form said article.
 9. The process as setforth in claim 8 wherein said article is an ophthalmic quality lensblank.
 10. The process as set forth in claim 8 wherein said concentratecomprises 40 parts of the product of reaction of equimolar quantities ofpropylene glycol with maleic anhydride, about 0.9 parts cobalt acetylacetonate, and about 0.07 parts copper acetyl acetonate.
 11. The processas set forth in claim 8 wherein about 0.10 parts concentrate is mixedwith 16 parts resin.